There are many processes in which it is desired to bring together firstly a solid phase material and secondly a fluid phase material in such a manner that the fluid phase material flows through, past or into, the solid phase material. Some of these are mentioned below. However, it is to be emphasized that the apparatus and method disclosed herein are believed potentially applicable to a broader range of materials and applications than the specific examples given.
A process of great practical importance is drying. For example, solid fuels used in combustion processes, such as brown and black coal, have often to be dried before combustion, and it is known to pass through beds of such materials combustor flue gases or gases indirectly heated by the combustion process.
Another essentially physical process class in which it may be desired to pass a fluid through a solid-phase material is heat exchange between a solid phase material and either a liquid or gas. As an example of a case where the fluid is a gas, U.S. Pat. No. 4,349,367 describes a method of recovering waste heat from furnace flue gases using a granular heat exchange means. This method involves passing gases from a furnace exhaust through a first bed of granular heat exchange medium so as to heat the medium. The heated medium is then passed to a second heat exchange bed where air being supplied to the furnace for combustion is passed through the (heated) medium to preheat the air. In this manner a portion of the waste heat is returned to the furnace by way of incoming combustion air. The apparatus used in this method comprises a cylindrical vessel having an annular cavity through which the granular heat exchange medium passes. The sides of the annular cavity are defined by concentrically arranged sets of louvres which facilitate passage of the furnace exhaust gases radially through the heat exchange medium. This system requires the use of a granular medium which is chemically inert and resists attrition; gravel, stone aggregates, ceramics or other refractory materials are preferred. The cylindrical configuration is not necessarily ideal for all combinations of solid- and gas-phase throughput volumes.
A still further fluid/solid process of importance, and to which the invention described below has potential application, is dust removal from gases. One of the many classes of device for this process is the so-called “cleanable granular bed filter”, wherein gas-laden dust is passed through a particle-removing granular medium that may be circulated continuously or emptied periodically from the dust removal unit. More generally, the invention described below is believed to have potential applications in separation processes where a fluid—be it liquid-phase or gas-phase—is passed through a solid-phase material.
Gas/solid operations also include humidifying and dehumidifying, and the invention herein described may find application in such operations also.
Finally, there are very many processes in which it is desired to pass a fluid through a solid-phase material in order to promote a chemical reaction. The invention described below is also potentially applicable as a reactor for some classes of fluid/solid reactions. The solid phase material could be a reactant or could be a catalyst that requires at intervals to be removed from a reactor vessel and replaced, and the invention can apply to both cases.
It is desirable in all of the application areas mentioned above for compact equipment whose basic design can be readily adapted to provide for particular combinations of fluid and solid material throughput. Furthermore, there is a need in at least some of these application areas for equipment whose design is comparatively easy to adapt for satisfactory flow of the solid phase material passing therethrough.